Selection system



Aug. 10, 1943. N. l. HALL 2,326,453

SELECTION SYSTEM Filed Feb. 17, 1942 3 Sheets-Sheet 1 FIG.

NON

NUMERICAL SW] TCHING STAGE 3 3 k Q I INVENTO R N./.HALL

ATTORNEY Aug. 10, 1943. N. I. HALL SELECTION SYSTEM Filed Feb. 17, 1942 3 Sheets-Sheet 2 INVEN TOR Ml. HALL A T TORNE Y Aug. 10, 19430 N. HALL SELECTION SYSTEM Filed Feb. 17, 1942 3 Sheets-Sheet 3 ATTORNEY Patented Aug. 10, 1943 2 326,458 SELECTION SYSTEM Nathan I. .Hall, Morristown, N. J as'sig'nor to, I Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York a 7 Application February-17, 1942, Serial No. 431,235

6 Claims.

This invention relates to selection systems and particularly to systems of this character when used for the purpose of establishing telephone or other communication connections.

The objects of the invention are to minimizeas much as possible the common controlling equip ment used in the establishment of connections through selective switching stages; to invest the in any of the terminating switches, thus prepare ing all of these channels for seizure. Thereafter a desired outgoingtrunk is chosen by a simplified marker, which seizes it in accordance with the digits of the received designation, and an ,electrical condition is placed upon said outgoing:

trunk. This condition causes aselective operation to proceed through the stage in the opposite switching stages with the faculty of performing theirown testing, selecting, and switch-operating functions; to simplify the controlling and switchoperating equipment; and in other respects .to realize improvements and advantages 'insystems of this general character. 1

It has been the practice heretofore in automatic telephone switching systems andparticug larly in those employing stages of crossbar direction for the purpose of energizing the hold. magnets of the successive switchesto seize theparticulariclle channel which extends between switchesfor establishing connections to provide common senders and markers for performing the numerous controlling and operating functions involved in the establishment of a telephone connection through the switching stages. Usually the marker, which is common to one .or'more stages of crossbar switches, receives the designation information from thesender, associates 'itself through frame connectors with the desired frames of. crossbar switches, tests thevarious serially related links extending :throughthese switches, and then, having found an idle channel, proceeds to operate the magnets of the switches to extend. the incoming circuit over the idle channel through the switching stages to the desired outgoing circuit.

According to the foregoing objects vof "the present invention advantages are. realized over these prior switching systems by means of a new and improved system in which the testing and switch-operating functionsare removed from the common controlling markers andare vested in the switches themselves. More specifically the presence of a call on a particular trunk incoming to'and appearing inv a particularone of a plurality of originating crossbar switches. at the switching stage causes an automatic testing operation to proceed through the. successive switches of the stage to determine all of the idle channels extending fromsaid particular originat: ing switch over links through the following intermediate switches and thence over linkslto all of the terminating switches of the stage. test progresses the select magnetsof the originating, intermediate, and terminating switches are operated corresponding to all idle channels that might be used in the extension of the inoming trunk to ,anyoutgoing trunk appearing As the 7 the seized outgoing trunk and theincoming trunk on which the call appears.

The operation of these hold magnets completes the connection through the switching stage, and all of the other a prepared switches are .restored to their normal condition. I

Thelforegoing and other features of the inv ene tion will be discussed more fully in the following detailed specification. V s

In the drawings accompanying the specifications, Figs. 1 2'and 3, when arranged as illus-. trated in Fig. 4, disclose a portion of an auto matic telephone system incorporating the features of this invention.

Fig. 1 shows anon-numericalfswitchmg stage" for extending subscribers lines over trunks to the originating switches of a selective switching stage. Two of these originating switchesare dis v closed in this figure. Y

Fig. 2 shows two of the intermediate switches and two of the final switches of the selective switching stage together with a number of outgoing trunks; and M Fig.3 discloses (in diagrammaticmanner) a sender-markerffor controlling. the switches of I 7 said selective stage.

While the invention is not necessarily limited to selective systems in which any specific-type of switch is used for performing the switching operations, it is particularly useful in such systems when switches of the. crossbar type areemployed. For a better understanding of the construction and operation of crossbar switches and of s the various circuits and mechanisms used in controlling them in the establishment of, telephone connections, reference may behad to the patent 1 to -Reynolds'2,021,329 of November 19,1935, and to the patents to Carpenter 2,093,117of September 14, 1937, and 2,235,803 of March 18 1941.

Referring to the drawings, the incomingtrunks, such as trunks'lll2, I03, I04, I05, appear in and are distributed among aplurality of first or originating crossbar switches in the selective switching stage. These trunks may com from the switch Ilil, and it will be noted that each trunk appears in only one or the originating switches. In addition to the originating or first switches the frame of the switching stage,- there are a plurality of intermediate switches and a plurality of'final or terminating switches. If it is assumed that there are ten originating switches; it is also convenient to assume that there are likewise ten intermediate switches 200 and 26!, etc'., and'similarly Iten terminating switches I92, 203, etc.

y The switches of the stage are interconnected with link circuits which are connectable in serial relation to 'form channels extending through the stage from the incoming trunks on the oneside to the outgoing trunks'o-ni the other side. These links are so distributed that it is possible to form achannel-between any trunk-incoming toany a originating switch and any trunkoutgcing from' any terminating switch. For example, the origihating switch. I95 hasten link circuits distribute respectively among the ten intermediate switches 2M; 291. As illustrated the link I I 0 extends a from the originating switch [65 to the intermediate switch 209,,andthe link I I I extends from originating switch N to, the intermediate switch Similarly links H2 and H3 extend between switch Ill! and switches 2G0. and 28L respectively. In like manner switches I05 and It! are provided with eight other links extending respectiyely to the eight other intermediate switches, anda similar distribution is true or the links extending from the eight other originating switches (not shown) to the ten intermediate switches In ."the' same manner the ten intermediate switches 28G, 29!, etc are connected to the terminating switches bylink' circuits, each intermediate switch having a link'circult extendingtc each of, the terminating switches 252, 203;, etc. As illustrated, the link 294 au io: interconnect the intermediate switch 20!! and'the terminating switches .292 and 233, respectively; and the iinkszt' and interconnectin the intermediate switch so: "and the terminating switches 262 and 203, respectively. Tnefout'gcing trunks. 208,138, 2H! and 2H are dlstributed among the terminating switches, each trunk appearin'g 'in afsingle switch andbeing. accessible to the ten linkincoming to such switch.

The crossbar switches are prcvi'dedwlth select magnets-each of which lsfllndivldualfto anLincoming circuit'and serves when energized to prepareitne switch for subsequently-connecting the inccmil cult to anycne of the outgoing circuits. For example, the originating swltcn'let is: provided with select magnets l M and I I5, which are individual respectively the incoming trunks I02 and. It: and serve to prepare the'switch for extending these truziksoyer any of the outgoing links. The intermediate switch zoos provided with select magnets 2H! and H3 which 'arein dividual' respectively tot-he, incoming links. Ill and H21 Likewise'the terminating switch 202 is provided with select magnets 2M and 25 which are individual respectively to the incoming links 294 and 206. The switches are also provided with hold magnets, one for each of the outgoing circuits. When one of these hold magnets is on erated following the previous 'energization' of select magnet, the takes place, ,and the incoming circuit represented bythe energized select Tmagnet is con nected to the outgoing circuit individual to the energized hold magnet. Thereafter the select magnet may be deenergized, the connection being held by the continued energization otthe bold magnet. In the switch I66 the hold magnets HG 'ahdIII "are individual res ectively to the out going links I and I l i in the switch zoo the hold to the outgoing links 295 and 235; and in the terminating switch 252 the hold magnets 2 I8 and 2 l9 areindividual respectively to th outgoing trunks Zil la'nd 299. L

.In addition to the select magnets, the. intermediate and final switches are provided with space-discharge tubes, there being one ofthese tubes for. each select magnet. Forexample, tubes 220 and 221 are individual respectively to the select magnets 2!: and2'l3, and tubes 222 and 223 are individual respectively tofthe select magnets 2| 4 and H5. Thepurpose of these tubes is to enable the simultaneous preparation of all the switches in the stage so that a connection may subsequently be completed fromiany incoming trunk through an idle channel to any desired outgoing trunk. This preparation is made by energ izing all of the select magnets representing links .in idle channels. Since; howeventhere may be fully operated tube brings, about; the energization of'the associated selectmagnet to prepare the switch for that particular channel while the other channels through the same switch remain disl .The testing and switch preparing operation is initiated at the calling lncoming'trunk' a pearing in. a particular one of the originating switches by applying an'electrical condition to the calling trunk; This condition causes a test potential to be projected simultaneously over all links outgoing from the said particular originating switch to all of the ten intermediate switches in which these links appear, causingthe operation of the corresponding select tubes and magnets." At each of the interme'diateswitches the test potential isjurther projected over all idle links outgoing from such intermediate switch to the correspond ing terminating switches, causing the operation of theiassociated select tubes and magnets. Thus trunk the hold magnets in the terminating, intermediate, and originating switches, corresponding to a prepared idle channel extending between the calling originating trunk and the chosen-outgoing trunk, are operatedsuccessively to cause the seizure ofthis channel and the completio of the connection betweenthe trunks.

. The selection of a desired outgoing trunk group and the testing'of the group for an idle one is performed by a common sender-markermecha nism which is associated with the switching stage and is taken in use whenever a call is extended through the stage. .since the greater partofthe 225 "may be traced from batterylthrough the winding of said ,rel'a'y, conductor 221, contacts sists of a register mechanism 380 for receiving the digits transmitted from the calling subscriber and a testing mechanism 38! for testing the chosen group of outgoing trunks to locate an idle one. .Since the sender-marker is common to all of the trunks incoming to the switching stage a connector 3832 is provided for connecting the calling trunk to the sender-marker and excluding other trunks until the connected one has been served. Also trunkconnectors 363,384, etc., are provided for connecting the test and control leads from the sender-markerto the desired group of outgoing trunks. marker has access to the switching stage by way of connectorsSBS and 396 to perform certain con- Furthermore, the sender-.

trolling operations.

The outgoing trunksmay be arranged in any suitable manner, singly or in groups. -For-example, it will beassumed in thepresent discussion that trunks 288 and 2 I 0 are two trunks ofa group represented by a given-designation. This'group may, of course, containothertrunks as well as the two shown. Similarly the trunks 259 and H I belong to another trunk group. 7

A detailed descriptionoftheoperation willnow be given. For this purpose assume that the subscriber of line iiiii wishes to set up a telephone connection over the route-represented by the trunk group 258, 21a The initiation of the call causes. the operation of the non-numerical switching stage I 8| to extend the subscribers line over an idle incoming trunk, such as the trunk 92, to the directive switching stage. The

selection of the incoming trunkJiiZ also results in the operation of the connector switch 302 to associate the trunk with the sender-markertli'l'.

The subscribers line lfie is nowextendedto the impulse relay 368 in the sender-marker, and the subscriber proceeds to operate his dial H8 to transmit the digits representing the designation of the desired trunkgroup 208, 21c. The digit impulses are received by the relay 368, which in turn causes the setting of the registers The number of registers involved will usually be governed by the number of out-trunk groups from which selection must be made and this, of course, is a matter of choice. H l

At some suitable time following the seizure of the sender-marker 391, the connectors3Q5 and 38B are operated to cause the operation of the battery supply relays/24 and 225 associated with the switching stage The circuitfor relay-224 may be traced frombattery through the winding oi"- the relay, conductor 2'35 through the contacts of connector 3&5 to ground at the'contact'o'f the relay 399 in the marker, which has-been operated at thistime, Similarly, the circuit for relay incoming link lit for connection to any idle of connector 395- to ground at the contact of relay 309.

Also at any suitable time following the seizure of the sender-marker 307, an electrical condition is placed upon the calling incoming trunk 102 tor the purpose of initiating the testing operation in the switching stage. Tothis end. the

"sender-marker operates the select' magnet lll I individual to the inccmingtrunk I02 in a'c'ircult traceable from battery through the winding r of said magnet, conductor ll9'through the connector 3M, conductor 3% through the contacts Magnet H4 of operated relay 3 to ground. prepares the switch for connecting the incoming trunk I92 to any one of. the ten'outgoi-ng links Magnet 1M also closes a circuit for no, I H. impressing a potential upon the control conductors-of, all idle links in the group He, HI. If these links are idle theyare so identified by the deenergized condition of their holding magnets i It, I 11, whereas bus-y links have their hold magnets energized.

. Assumethat at the tirne the test is made both I of the links H3 and! are idle. Since link starting cathodes of all ten tubes 22!), 22l,.etc.

If, there'-- fore, positive potential is applied over corresponding links to the starting-"anodes of two. ormore through an inductance element 25!;

of these tubes at the same time; the first tube to start the ionizationof its control gap" causes arr-induced voltage in the element 23! which is applied to the starting cathodes of all tubesito prevent the ionization-of'the starting gap of'la second tube. In this way a single tube succeeds in completing the ionization of its control gap,

and the remaining tubes are locked1out. "If, as

assumed, the .tube 22d succeeds in ionizing its control gap theornain gap also, discharges, and a circuit is traceable from thefpositive pole-of battery 232, contacts of relay 224; main anode- 233, main cathode 235, winding of select magnet; M2 to the negative pole of battery. 'The magnet 2H2 operates in this circuit and -prepares the of the ten outgoing links 294, 205;

Link! alsobeing idle at this,time ,--a circuitg .is closedfrom battery l ilover conductor- 122,

contacts of select magnet H4, back contacts: of magnet iii, conductor l 12ito the starting anode of tube 235' Tube. 235 operates in the'manner described, and a circuit is closed f-rom positive pole-oi battery. 232, contacts oi' relay 224,xcon+ ductor 238, main anode and cathode of tube'Z35 through the winding of select magnet 237 to battery. Magnet 23]. operates "and prepares the switch el for connecting the incoming link, ;I H

to any idle one of the ten outgoing links 385,291.

The test circuits thus extended from-the call:

ingincoming. trunk Hi2 over idle links to corree I sponding ones of the intermediate switches-2G0; 2 0! are also further extended ,oyer idle linksto the'terminating switchesj202 2ii3. .Forexample, 2''

one

:4 V V .the positive potential applied by the battery I to the control conductor I23 or link I I0 causes minating switches.

current to flow over conductor I22 through the contacts of magnet II4, normal contacts of magnet 6,.conductor I23 through. the unidirectional element 238, resistor 264 to ground. Current flow ing inthe resistor 264 applies a corresponding potential over conductor 239, back contacts of hold magne :2I6, assuming the link 204 to be idle, conductor 240 thence to the starting anode 24I of the tube 222; This potential, when added to the negatiye potential ofbattery 202,. which is applied through the common inductance 243 to the starting cathode 244, is sufiicient to ionize the control Zap comprising anode 2 and cathode 244. The

inductance 243 serves as explained to prevent more than one tube from completing the ionization, of its control gap. When tube 222 ionizes its control gap, a circuit is completed for the flow of current from the positive pole of battery 245, contacts of relay 225, conductor 246, main anode 241, main cathode 240 through the windingof select magnet 2I4 to the negative pole of battery.

. Magnet 2 I4 energizes and prepares the terminating switch 202 for connecting theincoming link 204 to any one of the ten trunks 208, 239, outgoing from said terminating'switch. If at the same time the link 205 is idle,'-the potential impressed upon conductor 230 is applied through the back contacts of magnet 2i! over conductor 252 to operate the tube 253 at the terminating switch 203. Tube 253 causes the operation of select magnet 254 in an obvious circuit, and the switch 203 is prepared to connect the links 2&5 to any one of the idle outgoing trunk 2I0, 2II. Also the positive potential applied over conductor I22 and over conductor I24 causes current to flow through theunidirectional element 243 and resistor to ground. Consequently a positive po tential is applied to the conductor 25I which is extended through the back contacts of the hold magnets of all idle links to the corresponding ter If,- for example, link 205 is idle, this potential is applied through the normal contacts of hold magnet 255, conductor 256 to the starting anode of the tube 223. Similarly if link 201 is idle, the potential is applied through the normal contacts of hold magnet 251, conductor 258 to the starting anode of tube 250. And the same is true of all other idle links in the switch 20!. Thus a positive potential may be applied to the starting anodes of a plurality of tubes in each of the final switches. A above explained, however, only one tube in each switch is permitted to ionize; so that only one select magnet can be energized. This precaution provides against the possibility of extending a connection to a single outgoing trunk over two or Imore link channels It was assumed that the tube 222 of switch 202 succeeded in ionizing,and it may also be assumed that tube 253 is the successful one in the switch 203. Therefore, the

7 select magnets 2H and 254 of'switches 202 and 203 are energized to prepare-for the selection of trunks outgoing from these switches. Similarly there may be one select magnet energized in each of a number of the remaining eight terminating switches to prepare the switches for the selection of the corresponding outgoing trunks.

Thus the testing operation has been completed in the switching stage, and the switches have bee-n prepared by the energization of their select mag- .netsso-that it is possible by the subsequent operation of the proper hold magnets to establisha connection over any idle channel, if one exists,

' links.

eration having been completed in the switching stage, a circuit is completed for placing an electrical condition on the chosen trunk-208 and for operating the hold magnet thereof. This circuit may be traced from ground through the contacts of relay'3I3, conductor 3 through the contacts of connector 303, testconductor260 through the winding of hold magnet2l8 to battery. Magnet 2I8 operates and causes the closure of the cross point contacts to connect the link circuit204 to the chosen outgoing trunk 208. This results'in the extension of the ground potential on conductor 260 through the cross-point contacts of'the switch 202 thence over conductor 25I through the Winding of the hold magnet 2I5 to battery. Magnet 2I6 operates and closes the cross-point contacts to connect the link circuit I I0 to the link circuit 204, and the ground potential on conductor 26I is extended through the contacts of the switch 200 over conductor 262 through the winding of the hold magnet I I6 to battery. Magnet IIE operatesand closes the cross-point contacts of'the switch I06 to connect the incoming trunk I02 to the link IIO. Also the ground potential on conductor 262 is extended through the cross-point contacts of the switch I05 to the test conductor I 25. In thefwell-know'n-manner a ground potential is applied to the conductor I25 from the control circuits of the trunk I02, and this potential is extended forward through the successive switches to maintain the hold magnets IIB, 2I6 and 2! in their energized condition in dependently of the sender-marker.

The connection has now been extended from the incoming trunk I02 to the outgoing trunk 208, and the sender-marker may be released by releasing the connectors'302, 305 and 306 and the trunk connector 303. When relays ,3I I and 303 are released in the sender-marker, the select magnet H4 and relays 224 and 225 deenergize. Magnet II4 disconnects the battery'IZO from all idle The release of relay 224 opens the circuits of select magnets 2I2, 231 and all other intermediate switch-select magnets that may have been operated in the preparation of the idle channels. Similarly the release of relay 225 opens the circuitsof select magnets 2I4 and 25.30 and all other operated select magnets in the final switches. The connection through the switching stage is now held solely by the hold magnets of the switches I06, 200 and 202, and all other switches and magnets are restored to their normal con- V dition ready for subsequent use.

is released inany well-known manner by the re- At the end of the conversation the connection cathode is disclosed in the No 2,273,958 of Feb. 24, 19 1-2. QlWhat is claimed is:

ing a plurality of originating, intermediate, and terminating switches, incoming trunksdistributed among said originating switches, outgoing trunks distributed among said terminating switches, links extending from each originating switch to each intermediate switch, links extendl..In combination, a switching stagecompris-l patent to Holden,

ing from each intermediate switch to each terminating switch, said switches when operated serving to connect the incoming trunks to the outgoing trunks over channels comprising serially related links, means for seizing any incoming trunk appearing in any particular one of said originating switches, means for testing all channels extending from said particular originating switch through said intermediate switches to said terminating switches and for preparing said switches for operation to seize all channels found to be'idle, means for seizing a desired one of said outgoing trunks, and means for operating the prepared switches corresponding, to an idle channel extending between the seized'incor'ningrially related links, means for seizing any incoming line appearing in any particuiar one of said originating switches, meansior placing an electrical condition on the seized'incoming line,1

means responsive to said electrical condition for automatically testing the links of all channels extending from said particular orginating switch through said intermediateswitches to said terminating switches and for preparing for operation the switches corresponding to all channels found to be idle, means for seizing any particular one of said outgoing lines, and means for operating the prepared switches corresponding to an idle channel extending between the seized incoming line and said outgoing line to establish a connection between such lines over said idle channel.

In combination, a switching stage'comprising a plurality of originating; intermediate, and terminating switches, incoming trunks distributed among said originating switches, outgoing trunks distributed among said terminating switches, links extending from said originating switch to each intermediate switch, links eX-. tending from each intermediate switch to each terminating switch, said switches when oper-i ated serving to connect the incoming trunks to the outgoing trunks over channels comprising serially related links, means for seizing any incoming trunk appearing in any particular one of said originating switches, means for testing all channels extending from said particular originating switch through said intermediate switches to said terminating switches and for r {or energizing the hold magnets oi the prepared Y r for operating insuccessionztheprepared. torminatingJintermediate and originating switches oorespondin'g to an idleflc'hannel ,Xte'ndingQbe-L tweedtheseized incomingfand outgoing, trunks; to establisha connection betweensaid't over said idle channel;-

4." In combinationa switching stage compri's.

ing a plurality of originating," intermediate, and

terminating switches, incoming trunks distrib'- uted among'said originating switches, outgoing 'r trunks distributed among said terminating switches, links extending from each originating switch to each intermediate switch, links extending from eachintermediate switch to each 1 i terminating switch,s'aid switches when oper, 'ated serving to connect the 'incomingtrunks to theoutgoing trunks over channels comprising serially relatedlinks, means'for seizing any incoming trunk appearing in any particular-one of said originating. switches, means for causing a testing operation to progress from said particularoriginating switch through said intermedi-' ate switches to all of said terminatingswitche's for testing all channels extending from' said particular originating switch throughsaid'i ntermediate switches to,the terminating switches and for preparing said switches ioroperation -to seize all channels found to be idle asa result o'f-Q I said test, means for seizinga particular one of 1 said outgoing trunks, and means for operating he P oper SWiliQhQS' corresponding to an idle channel extending between the seized incoming trunk and the said particular outgoing trunk to establish a connection between such trunks over saididle channel 5. In combinatiom'a-switching stage'compris' ing a plurality of originating," intermediate and terminating crossbar switches, each having select and hold magnets, incoming lines appearing in and distributedfamong I said originating switches, outgoing lines' appearing in and'dis tributed among said terminating switches, links extending from each originating to each intermediate switch, links, extending from cachintermediate switch to each terminating switch, said switches being operable to connect themcoming lines to the outgoing lines over channels 7 comprising said linkslin' serial relation, means" for seizing any incoming line, means for testing r the channels extending from the particular orig-' inating switch in which the seized incoming-line:

appears through said intermediate switches to said terminating switchesand for energizing the select magnets of said switches to, prepare said switches for operation to seize-all channels found to be in an idle condition, means for seizing a desired one of saidoutgoing lines, and. means switchescorresponding to an idle channelextending between the seized incoming andout going lines to establish a connection over said idle channel.

6. In combination, a switching stage comprising a, plurality of originating, intermediate} and terminatingswitches, incomingtrunks distrib- I switch to each intermediate switch, links extend ing from eachintermediate switch toteach terminating. switch, said switches when operated serving to connect theincoming trunks to the outgoing trunks over channels comprising serially related'links, :means for seizing any incoming trunk appearing in any particular one of s'a'fd meansf-fqitesting allchannel's a'rtefidjng fmm saftf particular orig mating" swit'bh' through; said intermediate siwithesjtoj sid terminating s witchesia'nd." for prepafing's'aid Switches forf operation to s ize" all channels found to be idle; means controlled i'naccordance with a desired id g's' ignafidfi for 6 r r j zzeg-fi sei zi'hg a partieul'ar (me of saikfbtiiagoig fir u'uk," and means for operating the pre ared switchescorrespgnding tq an idle chahne'f kt rfdifig' fietwn' me seized incdming and autgqmg trunks tolest'abli'sri a telephone connection over said 

